U.S. patent number 7,635,794 [Application Number 11/571,395] was granted by the patent office on 2009-12-22 for method for metathesis of compounds comprising an olefinic double bond, in particular olefins.
This patent grant is currently assigned to CPE Lyon Formation Continue ET Recherche-CPE Lyon FCR. Invention is credited to Jean-Marie Basset, Christophe Coperet, Erwan Le Roux, Mostafa Taoufik, Jean Thivolle-Cazat.
United States Patent |
7,635,794 |
Basset , et al. |
December 22, 2009 |
Method for metathesis of compounds comprising an olefinic double
bond, in particular olefins
Abstract
The invention relates to a method for metathesis of one or
several reagents comprising a linear or branched hydrocarbon chain
containing a double olefinic bond Csp.sup.2.dbd.Csp.sup.2
consisting in reacting said reagent or reagents with a supported
metal compound comprising an aluminum oxide-based support to which
a tungsten hydride is grafted. Typically, each said reagent or
reagents comprises from 2 to 30 carbon atoms. The reagent can be
embodied in the form of olefin. The inventive method can be used,
for example for producing propylene from ethylene and butane.
Inventors: |
Basset; Jean-Marie (Caluire Et
Cuire, FR), Thivolle-Cazat; Jean (Fontaines sur
Saone, FR), Taoufik; Mostafa (Villeurbanne,
FR), Le Roux; Erwan (Bergen, NO), Coperet;
Christophe (Lyons, FR) |
Assignee: |
CPE Lyon Formation Continue ET
Recherche-CPE Lyon FCR (Villeurbanne, FR)
|
Family
ID: |
34948455 |
Appl.
No.: |
11/571,395 |
Filed: |
July 1, 2005 |
PCT
Filed: |
July 01, 2005 |
PCT No.: |
PCT/FR2005/001692 |
371(c)(1),(2),(4) Date: |
February 06, 2008 |
PCT
Pub. No.: |
WO2006/013263 |
PCT
Pub. Date: |
February 09, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080255328 A1 |
Oct 16, 2008 |
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Foreign Application Priority Data
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Jul 2, 2004 [FR] |
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04 07396 |
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Current U.S.
Class: |
585/646;
585/643 |
Current CPC
Class: |
C07C
6/04 (20130101); C07C 6/04 (20130101); C07C
11/06 (20130101); C07C 2521/04 (20130101); C07C
2531/12 (20130101) |
Current International
Class: |
C07C
6/04 (20060101) |
Field of
Search: |
;585/643,646 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Levisalles et al, "Etudes sur le mecanisme de la metathese des
olefins i", 1980, pp. 195-207, vol. 192, No. 2, J. Organometallic
Chemistry, The Netherlands. cited by other .
Wengrovius et al, "Multiple metal-carbon bonds. 25. Preparation and
structure of tungsten neopentylidene hydride, neopentylidene
carbonyl, and neopentylidene ethylene complexes", 1982, p.
1739-1740, vol. 104, No. 6, Journal of the American Chemical
Society. cited by other.
|
Primary Examiner: Bullock; In Suk
Attorney, Agent or Firm: Schulman; B. Aaron Wright; Terry L.
Stites & Harbison PLLC
Claims
The invention claimed is:
1. A process for the metathesis of one or more reactants comprising
a linear or branched hydrocarbon chain comprising an olefinic
double bond Csp.sup.2.dbd.Csp.sup.2, in which this reactant or
these reactants is/are reacted in the presence of a supported metal
compound comprising a support based on aluminum oxide to which a
tungsten hydride is grafted.
2. The process as claimed in claim 1, in which the reactant or
reactants each comprise(s) from 2 to 30 carbon atoms.
3. The process as claimed in claim 1, in which the reactant is an
unsaturated, linear or branched, acyclic hydrocarbon, comprising a
Csp.sup.2.dbd.Csp.sup.2 double bond between two carbon atoms, of
empirical formula C.sub.nH.sub.2n, n being an integer ranging from
2 to 30.
4. The process as claimed in claim 1, in which ethylene and butene
are reacted to produce propylene.
5. The process as claimed in claim 1, in which the compound
corresponds to the formula R.sub.1R.sub.2C.dbd.CR.sub.3R.sub.4 in
which identical or different R.sub.i (i=1 to 4) substituents are
chosen from hydrogen atoms, saturated, linear or branched,
hydrocarbon groups and saturated cyclic hydrocarbon groups which
optionally carry hydrocarbon substituents and which can be
connected to the Csp.sup.2 carbon of the olefinic double bond
either directly or via a saturated hydrocarbon chain.
6. The process as claimed in claim 1, in which the compound
corresponds to the formula R.sub.1R.sub.2C.dbd.CR.sub.3R.sub.4 in
which identical or different R.sub.i (i=1 to 4) substituents are
chosen from hydrogen atoms, saturated, linear or branched,
hydrocarbon groups and aromatic rings which optionally carry
saturated hydrocarbon substituents and which can be connected to
the Csp.sup.2 carbon of the olefinic double bond either directly or
via a saturated hydrocarbon chain.
7. The process as claimed in claim 1, in which the degree of
oxidation of the tungsten has a value chosen within a range
extending from 2 to 6.
8. The process as claimed in claim 1, in which the tungsten atom is
bonded to one or more hydrogen atoms and optionally to one or more
hydrocarbon radicals R.
9. The process as claimed in claim 8, in which the hydrocarbon
radicals R are identical or different, saturated or unsaturated,
hydrocarbon radicals comprising from 1 to 20 carbon atoms and
optionally comprising silicon.
10. The process as claimed in claim 1, in which the tungsten
hydride is grafted to the support based on aluminum oxide according
to the following scheme: ##STR00005## in which W, Al, O and H
respectively represent tungsten, aluminum, oxygen and hydrogen
atoms, M represents an atom of one or more elements of another
oxide, R represents a hydrocarbon radical and x, y, w and z are
integers, the sum (w+x+y+z) of which is equal to 2 to 6, and with
x=1 to 3, y=1 to 5, w=0 to 4 and z=0 to 2, the --(Al--O) and
--(M--O) bonds representing one or more single or multiple bonds
respectively connecting the aluminum atom and the atom M to one of
the atomic constituents of the support based on aluminum oxide, in
particular to one of the oxygen atoms of this support.
11. The process as claimed claim 1, in which the support is chosen
from supports homogeneous in composition based on aluminum oxide
and from heterogeneous supports based on aluminum oxide comprising
aluminum oxide essentially at the surface of said heterogeneous
supports.
12. The process as claimed in claim 1, in which the support
comprises aluminum oxide, mixed aluminum oxides or modified
aluminum oxides.
13. The process as claimed in claim 1, in which the reaction is
carried out at a temperature ranging from 20 to 600.degree. C.
14. The process as claimed in claim 1, in which the reaction is
carried out under an absolute pressure ranging from 0.01 to 8
MPa.
15. The process as claimed in claim 1, in which the metal compound
is regenerated in the presence of hydrogen.
16. The process as claimed in claim 15, in which the regeneration
is carried out at a temperature of between 50 and 300.degree.
C.
17. The process as claimed in claim 15, in which the regeneration
is carried out with a hydrogen pressure ranging from 0.01 to 10
MPa.
18. The process as claimed in claim 7, wherein the range extends
from 4 to 6.
19. The process as claimed in claim 9, wherein the hydrocarbon
radicals comprise 1 to 10 carbon atoms.
20. The process as claimed in claim 13, wherein the temperature
ranges from 20 to 350.degree. C.
21. The process as claimed in claim 13, wherein the temperature
ranges from 50 to 300.degree. C.
22. The process as claimed in claim 13, wherein the temperature
ranges from 80 to 200.degree. C.
23. The process as claimed in claim 14, wherein the absolute
pressure ranges from 0.01 MPa to 1 MPa.
24. The process as claimed in claim 14, wherein the absolute
pressure ranges from 0.1 MPa to 0.5 MPa.
25. The process as claimed in claim 16, wherein the temperature is
between 80 and 200.degree. C.
26. The process as claimed in claim 17, wherein the hydrogen
pressure ranges from 0.1 to 2 MPa.
Description
The present invention relates to a process for the metathesis of
one or more reactants comprising an olefinic structure.
The reaction for the metathesis of olefins was discovered
approximately 40 years ago; it is a reversible transalkylidenation
reaction, that is to say a reversible reaction for exchange of
alkylidene groups within an olefin (self-metathesis) or a mixture
of olefins (crossed metathesis); in some cases, these olefins can
comprise functional groups. Equations (1) and (2) respectively
represent the self-metathesis and crossed metathesis reactions:
##STR00001## where R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5,
R.sub.6, R.sub.7 and R.sub.8 represent hydrogen atoms or
functionalized or nonfunctionalized hydrocarbon groups.
The first catalysts described by Philips Petroleum, who discovered
this reaction, were of heterogeneous type; they were composed
essentially of MoO.sub.3 deposited on silica or alumina, operating
at approximately 150-200.degree. C. but unstable and deactivating,
or of WO.sub.3 deposited on the same supports, operating at
approximately 400-450.degree. C.; the latter system,
WO.sub.3/SiO.sub.2, remains the catalyst used industrially. The
disadvantages of the latter system include the high temperatures,
both for the reaction itself and for the regeneration of the
catalyst.
It would be highly advantageous to have available a heterogeneous
catalytic system effective in the meta-thesis of reactants
comprising an olefinic structure, e.g. olefins, which is capable of
operating at relatively low temperature and which can be
regenerated at moderate temperature.
An objective of the invention is thus to provide an effective
process for the metathesis of reactants comprising an olefinic
structure, e.g. olefins, using a catalyst which is capable of
operating at relatively low temperature.
Another objective of the invention is to provide such a process in
which the catalyst can be regenerated at moderate temperature.
A subject matter of the present invention is thus a process for the
metathesis of one or more, preferably one or two, reactants
comprising a linear or branched hydrocarbon chain comprising an
olefinic double bond Csp.sup.2.dbd.Csp.sup.2 (olefinic structure),
in which this reactant or these reactants is/are brought into the
presence of a supported metal compound comprising a support based
on aluminum oxide to which a tungsten hydride is grafted.
The olefinic double bond is included in a linear or branched
hydrocarbon chain of formula R.sub.1R.sub.2C.dbd.CR.sub.3R.sub.4
comprising an olefinic double bond Csp.sup.2.dbd.Csp.sup.2 and
identical or different substituents R.sub.i (i=1 to 4) on these
carbons.
According to one characteristic of the invention, each reactant
comprises, in total, from 2 to 30 carbon atoms.
According to a first embodiment, the invention relates to the
metathesis of one or more olefins or alkenes, namely unsaturated,
linear or branched, acyclic hydrocarbon(s), comprising a
Csp.sup.2.dbd.Csp.sup.2 double bond between two carbon atoms, of
empirical formula C.sub.nH.sub.2n and preferably with n an integer
ranging from 2 to 30. The R.sub.i substituents can, for example, be
of the hydrogen, methyl, ethyl, propyl or isopropyl, butyl,
sec-butyl or isobutyl, or pentyl, sec-pentyl, isopentyl or
neopentyl type.
According to a specific aspect of this embodiment, the invention
relates to a process for the production of propylene in which
ethylene and butene are reacted in the presence of the supported
metal compound comprising a support based on aluminum oxide to
which a tungsten hydride is grafted.
According to a second embodiment, the reactant or reactants
comprise(s) identical or different R.sub.i substituents chosen from
hydrogen atoms, saturated, linear or branched, hydrocarbon groups
and saturated cyclic hydrocarbon groups which optionally carry
hydrocarbon substituents and which can be connected to the
Csp.sup.2 carbon of the olefinic double bond either directly or via
a saturated hydrocarbon chain. The cyclic R.sub.i hydrocarbon
substituents can, for example, be of the cyclopropyl, cyclobutyl,
cyclopentyl or cyclohexyl type and the like or of substituted
cyclic type, such as methylcycloalkyl, ethylcycloalkyl,
methylenecycloalkyl or of formula --(CH.sub.2).sub.n-cycloalkyl. In
addition to hydrogen, the other substituents optionally present
can, for example, be of the methyl, ethyl, propyl or isopropyl,
butyl, sec-butyl or isobutyl, or pentyl, sec-pentyl, isopentyl or
neopentyl type.
According to a third embodiment, the reactant or reactants
comprise(s) identical or different R.sub.i substituents chosen from
hydrogen atoms, saturated, linear or branched, hydrocarbon groups
and aromatic rings which optionally carry saturated hydrocarbon
substituents and which can be connected to the Csp.sup.2 carbon of
the olefinic double bond either directly or via a saturated
hydrocarbon chain. The R.sub.i substituents comprising aromatic
rings can, for example, be of the phenyl, tolyl, benzyl, xylyl or
biphenyl type or of formula --(CH.sub.2).sub.n-aryl. In addition to
hydrogen, the other substituents optionally present can, for
example, be of the methyl, ethyl, propyl or isopropyl, butyl,
sec-butyl or isobutyl, or pentyl, sec-pentyl, isopentyl or
neopentyl type.
According to a fourth embodiment, different reactants chosen from
those described in the preceding three series are reacted
together.
The process of the invention can be carried out at a temperature
ranging from 20 to 600.degree. C. According to an advantageous
characteristic of the invention, the process is carried out at a
relatively low temperature ranging from 20 to 350.degree. C.,
preferably from 50 to 300.degree. C., better still from 80 to
200.degree. C.
According to another characteristic, the process is carried out
under an absolute pressure ranging from 0.01 to 8 MPa, preferably
from 0.01 to 1 MPa, better still from 0.1 to 0.5 MPa.
The reactant or reactants can be made use of in the gaseous or
liquid form.
The process can be carried out in the presence of hydrogen or of an
agent which forms hydrogen in situ. Thus, the process can be
carried out under a hydrogen partial pressure ranging from 0.001 to
0.1 MPa. Mention may be made, as agent which forms hydrogen in
situ, of cyclic compounds, such as cyclohexane,
decahydro-naphthalene and tetrahydronaphthalene.
According to an advantageous characteristic of the invention, the
catalyst can be reactivated or regenerated by bringing into contact
with hydrogen, in particular pure hydrogen or hydrogen diluted in a
neutral gas. The regeneration can be carried out with a hydrogen
pressure ranging from 0.01 to 10 MPa, preferably from 0.1 to 2 MPa.
It is possible to proceed in the following way. The feeding of the
reactor with reactant(s) is halted. Hydrogen is subsequently
injected and a hydrogen pressure is maintained for a time
sufficient to regenerate the catalyst. Before resuming the
metathesis reaction, it is preferable to drive off the excess
hydrogen by introducing a neutral gas, e.g. argon. The regeneration
temperature is advantageously between 50 and 300.degree. C.,
preferably between 80 and 200.degree. C.
The process of the invention can be carried out batchwise in a
static reactor. However, it is preferably carried out continuously
in a dynamic reactor.
The term "tungsten hydride grafted to a support based on aluminum
oxide" is understood to mean, generally, a tungsten atom bonded to
at least one hydrogen atom and, in particular by at least one
single bond, to said support.
The metal compound essentially comprises a tungsten hydride grafted
to a support based on aluminum oxide. In this compound, the support
can be any support based on aluminum oxide and more particularly
any support where the aluminum oxide is accessible in particular at
the surface of said support. Thus, the support can be chosen from
supports relatively homogeneous in composition based on aluminum
oxide, having in particular a composition based on aluminum oxide
relatively homogeneous throughout the body of the support, that is
to say from the core up to the surface of the support, and also
from heterogeneous supports based on aluminum oxide comprising
aluminum oxide essentially at the surface of the supports. In the
case of a heterogeneous support, the support can comprise aluminum
oxide deposited on, supported on or grafted to a mineral solid
which can itself be a solid inorganic support, in particular chosen
from metals, oxides or sulfides, and salts, for example from silica
and metal oxides.
The support can have a specific surface (B.E.T.) chosen within a
range extending from 0.1 to 1000 m.sup.2/g, preferably from 0.5 to
800 m.sup.2/g. The specific surface (B.E.T.) is measured according
to the standard ISO 9277 (1995).
The support can in particular comprise aluminum oxide, mixed
aluminum oxides or modified aluminum oxides, in particular modified
by one or more elements from Groups 15 to 17 of the Periodic Table
of the Elements (as defined by the IUPAC in 1991 in which the
groups are numbered from 1 to 18 and which is found, for example,
in "CRC Handbook of Chemistry and Physics", 76th edition
(1995-1996), by David R. Lide, published by CRC Press Inc.,
USA).
The term "aluminum oxide" (also known as simple alumina) is
understood to mean, generally, an aluminum oxide substantially
devoid of any other oxide (or comprising less than 2% by weight of
one or more other oxides present in the form of impurities). If it
comprises more than 2% by weight of one or more other oxides, then
it is generally convenient to regard the oxide as a mixed aluminum
oxide, that is to say an aluminum oxide combined with at least one
other oxide.
The support can preferably comprise aluminum oxide chosen from
porous aluminas, nonporous aluminas and mesoporous aluminas.
Porous aluminas are often referred to as "activated aluminas" or
"transition aluminas". They generally correspond to various
partially hydroxylated aluminum oxides Al.sub.2O.sub.3. They are
porous supports generally obtained by an "activation" treatment
comprising in particular a heat (or dehydration) treatment of a
precursor chosen from aluminum hydroxides, such as aluminum
trihydroxides, hydroxides of aluminum oxide or gelatinous aluminum
hydroxides. The activation treatment makes it possible to remove
the water present in the precursor but also, in part, the hydroxyl
groups, thus leaving behind a few residual hydroxyl groups and a
specific porous structure. The surface of the porous aluminas
generally comprises a complex mixture of aluminum and oxygen atoms
and of hydroxide ions which combine according to specific
crystalline forms and which in particular produce both acidic and
basic sites. It is thus possible to choose, as solid support, a
porous alumina from .gamma.-alumina (gamma-alumina), .eta.-alumina
(eta-alumina), .delta.-alumina (delta-alumina), .theta.-alumina
(theta-alumina), .kappa.-alumina (kappa-alumina), .rho.-alumina
(rho-alumina) and .chi.-alumina (chi-alumina) and preferably from
.gamma.-alumina and .eta.-alumina. These various crystalline forms
depend essentially on the choice of the precursor and of the
conditions of the activation treatment, in particular the
temperature and the pressure. The activation treatment can be
carried out, for example, under a stream of air or a stream of
another gas, in particular inert gas, at a temperature which can be
chosen within a range extending from 100 to 1000.degree. C.,
preferably from 200 to 1000.degree. C.
Use can also be made of porous aluminas or semiporous aluminas
prepared by an activation treatment as described above, in
particular at a temperature ranging from 600 to 1000.degree. C.
These porous or semiporous aluminas can comprise mixtures of porous
aluminas in at least one of the crystalline forms described above,
such as .gamma.-alumina, .eta.-alumina, .delta.-alumina,
.theta.-alumina, .kappa.-alumina, .rho.-alumina or .chi.-alumina,
with a nonporous alumina, in particular .alpha.-alumina, in
particular in a proportion of 20 to 80% by weight.
Porous aluminas are generally thermal decomposition products of
aluminum trihydroxides, hydroxides of aluminum oxide (or hydrates
of aluminum oxide) and gelatinous aluminum hydroxides (or alumina
gels).
Aluminum trihydroxides of general formula
Al(OH).sub.3.dbd.Al.sub.2O.sub.3.3H.sub.2O can exist in different
crystalline forms, such as gibbsite or hydrargillite
(.alpha.-Al(OH).sub.3), bayerite (.beta.-Al(OH).sub.3) or
nordstrandite. Aluminum trihydroxides can be obtained by
precipitation from aluminum salts in generally alkaline
solutions.
Hydroxides of aluminum oxide of general formula
AlO(OH).dbd.Al.sub.2O.sub.3.H.sub.2O can also exist in different
crystalline forms, such as diaspore (.beta.-AlO(OH)) or boehmite
(or .alpha.-AlO(OH)). Diaspore can occur in certain types of clay
and of bauxite and can be synthesized by heat treatment of gibbsite
at approximately 150.degree. C. or by hydrothermal treatment of
boehmite at 380.degree. C. under a pressure of 50 MPa. Boehmite can
be easily obtained by heating the gelatinous precipitate formed on
treating solutions of aluminum salts under cold conditions with
ammonia. Hydroxides of aluminum oxide can also be obtained by
hydrolysis of aluminum alkoxides.
Gelatinous aluminum hydroxides (or alumina gels) are generally
poly(aluminum hydroxide)s, in particular of general formula:
nAl(OH).sub.3(n-1)H.sub.2O (1) in which n is a number varying from
1 to 8. Geiatinous aluminum hydroxides can be obtained by one of
the processes chosen from the thermal decomposition of an aluminum
salt, such as aluminum chloride, the electrolysis of aluminum
salts, such as a mixture of aluminum sulfate and of alkali metal
sulfate, the hydrolysis of aluminum alkoxides, such as aluminum
methoxide, precipitation from aluminates, such as alkali metal or
alkaline earth metal aluminates, and precipitation from aluminum
salts, for example by bringing into contact aqueous solutions of
Al.sub.2(SO.sub.4).sub.3 and of ammonia, or of NaAlO.sub.2 and of
an acid, or of NaAlO.sub.2 and of Al.sub.2(SO.sub.4).sub.3, it
being possible for the precipitates thus obtained to be
subsequently subjected to aging and drying in order to remove the
water. Gelatinous aluminum hydroxides generally exist in the form
of an amorphous alumina gel, in particular in the form of a
pseudoboehmite.
The porous aluminas can have a specific surface (B.E.T.) chosen
within a range extending from 100 to 1000 m.sup.2/g, preferably
from 300 to 1000 m.sup.2/g, in particular from 300 to 800
m.sup.2/g, especially from 300 to 600 m.sup.2/g. They can in
addition exhibit a specific pore volume equal to or less than 1
cm.sup.3/g, preferably equal to or less than 0.9 cm.sup.3/g, in
particular equal to or less than 0.6 cm.sup.3/g.
The support can also comprise nonporous aluminas, preferably
.alpha.-alumina (alpha-alumina), generally known under the term of
"calcined alumina". .alpha.-Alumina exists in the natural state
under the term of "corundum". It can be synthesized generally by
heat treatment or calcination of a precursor chosen in particular
from aluminum salts, hydroxides of aluminum oxide, aluminum
trihydroxides and aluminum oxides, such as .gamma.-alumina, at a
temperature of greater than 1000.degree. C., preferably of greater
than 1100.degree. C. It can comprise impurities, such as other
oxides, for example Fe.sub.2O.sub.3, SiO.sub.2, TiO.sub.2, CaO,
Na.sub.2O, K.sub.2O, MgO, SrO, BaO and Li.sub.2O, in proportions of
less than 2%, preferably less than 1%, by weight. The nonporous
aluminas, such as .alpha.-alumina, can have a specific surface
(B.E.T.) chosen within a range extending from 0.1 to less than 300
m.sup.2/g, preferably from 0.5 to 300 m.sup.2/g, in particular from
0.5 to 250 m.sup.2/g.
The support can also comprise mesoporous aluminas having in
particular a specific surface (B.E.T.) chosen within a range
extending from 100 to 800 m.sup.2/g. The mesoporous aluminas
generally have pores with a width ranging from 2 nm to 0.05
.mu.m.
The support can also comprise mixed aluminum oxides. The term
"mixed aluminum oxides" is understood to mean, generally, aluminum
oxides combined with at least one other oxide in a proportion by
weight preferably from 2 to less than 80%, in particular from 2 to
less than 50%, especially from 2 to less than 40% or even from 2 to
less than 30%. The other oxide or oxides can be oxides of the
elements M chosen from the metals from Groups 1 to 13 and elements
from Group 14, with the exception of carbon, of the Periodic Table
of the Elements. More particularly, they can be oxides of the
elements M chosen from alkali metals, alkaline earth metals,
transition metals and elements from Groups 13 and 14 of said table,
with the exception of carbon. The transition metals generally
comprise the metals from Groups 3 to 11 of said table, in
particular elements 21 to 29, 39 to 47 and 57 to 79 (including
lanthanides) and the actinides. The other oxide or oxides of the
elements M are preferably chosen from the transition metals from
Groups 3 to 7, the lanthanides, the actinides and the elements from
Groups 13 and 14 of said table, with the exception of carbon. More
particularly, they can be chosen from silicon, boron, gallium,
germanium, titanium, zirconium, cerium, vanadium, niobium,
tantalum, chromium, molybdenum and tungsten oxides.
The mixed aluminum oxides can be chosen from anhydrous aluminates,
from spinels and from aluminosilicates. In particular, the
anhydrous aluminates can be chosen from anhydrous alkali metal
aluminates, such as anhydrous lithium aluminate (LiAlO.sub.2) or
anhydrous sodium aluminate (Na.sub.2O.Al.sub.2O.sub.3), and
anhydrous alkaline earth metal aluminates, such as anhydrous
tricalcium aluminate (3CaO.Al.sub.2O.sub.3) or anhydrous beryllium
aluminate (BeO.Al.sub.2O.sub.3). The spinels can be chosen in
particular from aluminum oxides combined with oxides of divalent
metals and in particular from magnesium spinel (MgAl.sub.2O.sub.4),
calcium spinel (CaAl.sub.2O.sub.4), zinc spinel
(ZnAl.sub.2O.sub.4), manganese spinel (MnAl.sub.2O.sub.4), iron
spinel (FeAl.sub.2O.sub.4) and cobalt spinel (CoAl.sub.2O.sub.4).
The alumino-silicates can be chosen in particular from clays, talc,
micas, feldspar, microporous aluminosilicates, in particular
molecular sieves, and zeolites.
The support can also comprise modified aluminum oxides, in
particular modified by one or more elements from Groups 15 to 17,
preferably Groups 16 to 17, of the Periodic Table of the Elements,
for example phosphorus, sulfur, fluorine or chlorine. The support
can in particular comprise alumina superacids or aluminum oxides
which are sulfated, sulfided, chlorinated or fluorinated.
The support can be a support homogeneous in composition, in
particular throughout the body of the support. It can also be a
heterogeneous support based on aluminum oxide, in which support the
aluminum oxide, the mixed aluminum oxides or the modified aluminum
oxides, as described above, are essentially positioned at the
surface of the support and the core of the support is essentially
composed of a mineral solid chosen in particular from metals,
oxides or sulfides, and salts, such as silica or metal oxides. The
heterogeneous support can be prepared by dispersing over, by
precipitating on and/or by grafting to the mineral solid one of the
precursors of the compounds based on aluminum oxide mentioned
above. The precursors can in particular be chosen from aluminum
hydroxides, in particular from aluminum trihydroxides, hydroxides
of aluminum oxide and gelatinous aluminum hydroxides. Preference is
given to gelatinous aluminum hydroxides, such as described above,
known under the term of alumina gels or of amorphous aluminas. A
heterogeneous support can be prepared in particular by employing
such a precursor by way of a sol-gel or using an organo-metallic
compound, which facilitates in particular the grafting to the
mineral solid.
The compound according to the invention is generally provided in
the form of particles which can have any shape and any size, in
particular a mean size ranging from 10 nm to 5 mm, preferably from
20 nm to 4 mm. The particles of the support can be provided as is
or can be shaped so as to have a specific shape, in particular a
spherical, spheroidal, hemispherical, hemispheroidal, cylindrical
or cubic shape or the shape of rings, pellets, disks or
granules.
The compound according to the invention essentially comprises a
tungsten hydride grafted to the support based on aluminum oxide.
The degree of oxidation of the tungsten in the supported metal
compound can have a value chosen within a range extending from 2 to
6, preferably from 4 to 6. The tungsten atom is bonded in
particular to the solid support, in particular via at least one
single bond. It can in addition be bonded to one or more hydrogen
atoms via single bonds (W--H) and optionally to one or more
hydrocarbon radicals R, in particular via carbon-tungsten single or
multiple bonds. The number of hydrogen atoms bonded to a tungsten
atom depends on the degree of oxidation of the tungsten, on the
number of single bonds bonding said tungsten atom to the support
and optionally on the number of single or multiple bonds bonding
said tungsten atom to the hydrocarbon radical R. Thus, the number
of hydrogen atoms bonded to a tungsten atom can be at least equal
to 1 and at most equal to 5 and can preferably range from 1 to 4,
preferably from 1 to 3. The term "grafting of the tungsten hydride
to the solid support based on aluminum oxide" is understood to
mean, generally, that the tungsten atom is bonded via at least one
single bond to said support and more particularly via at least one
single bond (W--OAl) to at least one oxygen atom of the aluminum
oxide. The number of single bonds bonding the tungsten atom to the
support, in particular via a single bond (W--OAl), depends on the
degree of oxidation of the tungsten and on the number of the other
bonds bonding the tungsten atom and is generally equal to 1, 2 or
3.
The tungsten atom of the compound according to the invention can
optionally be bonded to one or more hydrocarbon radicals R via one
or more carbon-tungsten single, double or triple bonds. The
hydrocarbon radical or radicals R can be identical or different,
saturated or unsaturated, hydrocarbon radicals comprising in
particular from 1 to 20, preferably from 1 to 10, carbon atoms and
optionally comprising silicon, in particular in an organosilane
group. They can be chosen in particular from alicyclic or
aliphatic, in particular linear or branched, alkyl radicals, for
example alkyl, alkylidene or alkylidyne radicals, in particular
from C.sub.1 to C.sub.10 radicals, from aryl radicals, in
particular from C.sub.6 to C.sub.12 radicals, and from aralkyl,
aralkylidene or aralkylidyne radicals, in particular from C.sub.7
to C.sub.14 radicals.
The tungsten atom of the grafted tungsten hydride can be bonded to
the hydrocarbon radical R via one or more carbon-tungsten single,
double or triple bonds. A carbon-tungsten single bond, in
particular of .sigma. type, may be concerned: in this case, the
hydrocarbon radical R can be an alkyl radical, in particular a
linear or branched alkyl radical, or an aryl radical, for example,
the phenyl radical, or an aralkyl radical, for example the benzyl
radical or the radical of formula
C.sub.6H.sub.5--CH.sub.2--CH.sub.2--. The term "alkyl radical" is
understood to mean, generally, a monovalent aliphatic radical
originating from the removal of a hydrogen atom on a carbon atom of
the molecule of an alkane or of an alkene or of an alkyne or even
of an organosilane, for example a methyl (CH.sub.3--), ethyl
(C.sub.2H.sub.5--), propyl (C.sub.2H.sub.5--CH.sub.2--), neopentyl
((CH.sub.3).sub.3C--CH.sub.2--), allyl
(CH.sub.2.dbd.CH--CH.sub.2--), alkynyl (R--C.ident.C--), in
particular ethynyl (CH.ident.C--), or neosilyl
((CH.sub.3).sub.3Si--CH.sub.2--) radical. The alkyl radical can,
for example, be of formula R'--CH.sub.2-- where R' represents a
linear or branched alkyl radical.
A carbon-tungsten double bond, in particular of .pi. type, may also
be concerned: in this case, the hydrocarbon radical R can be an
alkylidene radical, in particular a linear or branched alkylidene
radical, or an aralkylidene radical. The term "alkylidene radical"
is understood to mean, generally, a divalent aliphatic radical
originating from the removal of two hydrogen atoms on the same
carbon atom of the molecule of an alkane or of an alkene or of an
alkyne or even of an organosilane, for example a methylidene
(CH.sub.2.dbd.), ethylidene (CH.sub.3--CH.dbd.), propylidene
(C.sub.2H.sub.5--CH.dbd.), neopentylidene
((CH.sub.3).sub.3C--CH.dbd.) or allylidene
(CH.sub.2.dbd.CH--CH.dbd.) radical. The alkylidene radical can, for
example, be of formula R'--CH.dbd. where R' represents a linear or
branched alkyl radical. The term "aralkylidene radical" is
understood to mean, generally, a divalent aliphatic radical
originating from the removal of two hydrogen atoms on the same
carbon of an alkyl, alkenyl or alkynyl radical connected to an
aromatic group.
A carbon-tungsten triple bond may also be concerned: in this case,
the hydrocarbon radical R can be an alkylidyne radical, in
particular a linear or branched alkylidyne radical, or an
aralkylidyne radical. The term "alkylidyne radical" is understood
to mean, generally, a trivalent aliphatic radical originating from
the removal of three hydrogen atoms on the same carbon atom of the
molecule of an alkane or of an alkene or of an alkyne or even of an
organosilane, for example an ethylidyne (CH.sub.3--C.ident.),
propylidyne (C.sub.2H.sub.5--C.ident.), neopentylidyne
((CH.sub.3).sub.3C--C.ident.) or allylidyne
(CH.sub.2.dbd.CH--C.ident.) radical. The alkylidyne radical can,
for example, be of formula R'--C.ident. where R' represents a
linear or branched alkyl radical. The term "aralkylidyne radical"
is understood to mean, generally, a trivalent aliphatic radical
originating from the removal of three hydrogen atoms on the same
carbon of an alkyl, alkenyl or alkynyl radical connected to an
aromatic group.
More particularly, the hydrocarbon radical R can be chosen from the
methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, neopentyl,
allyl, neopentylidene, allylidene, neopentylidyne and neosilyl
radicals.
The tungsten atom of the compound according to the invention can be
complexed by one or more hydrocarbon ligands, in particular
aromatic or carbonyl ligands.
The tungsten hydride grafted to the support based on aluminum oxide
can be represented diagrammatically by the following formula:
##STR00002## in which W, Al, O and H respectively represent
tungsten, aluminum, oxygen and hydrogen atoms, M represents an atom
of one or more elements of another oxide, such as defined above, R
represents a hydrocarbon radical, such as defined above, and x, y,
w and z are integers, the sum (w+x+y+z) of which is equal to 2 to
6, and with x=1 to 3, y=1 to 5, w=0 to 4 and z=0 to 2. In the
formula (2), the --(Al--O) and --(M--O) bonds represent one or more
single or multiple bonds respectively connecting the aluminum atom
and the atom M to one of the atomic constituents of the support
based on aluminum oxide, in particular to one of the oxygen atoms
of this support.
The compound according to the invention generally exhibits, by
infrared spectroscopy, one or more specific absorption bands of the
W--H bond, the frequency of which bands can vary according to the
coordination sphere of the tungsten and can depend in particular on
the number of bonds of the tungsten with the support, with the
hydrocarbon radicals R and with other hydrogen atoms. Thus, for
example, at least two absorption bands at 1903 and 1804 cm.sup.-1
have been found, which bands are specific in particular of the W--H
bond considered in particular in the environment of the W--OAl
bonds bonding the same tungsten atom to an oxygen atom itself
bonded to an aluminum atom of .alpha.-alumina. By way of
comparison, tungsten hydride grafted under the same conditions to a
silica support generally exhibits, by infrared spectroscopy, at
least one of the two absorption bands at 1940 and 1960 cm.sup.-1,
which bands are different from the above and which are in
particular specific of the W--H bond considered in particular in
the environment of the W--OSi bonds bonding the same tungsten atom
to an oxygen atom itself bonded to a silicon atom of the silica
support.
Another way of being able to characterize the presence of a W--H
bond in the compound according to the invention comes from a
measurement by proton Nuclear Magnetic Resonance (solid .sup.1H
NMR) at 500 MHz, where the value of the chemical shift of the
tungsten hydride (.delta..sub.W--H) is equal to 10.6 ppm (parts per
million).
The compound according to the invention can additionally comprise
an aluminum hydride, in particular at the surface of the support
and in particular in the vicinity of the grafted tungsten hydride.
It is believed that an aluminum hydride can be formed by opening of
an aluminoxane bridge (of formula Al--O--Al) present in particular
at the surface of the support and by reaction between a hydrogen
atom of a grafted tungsten hydride and the aluminoxane bridge thus
opened. A simple test for the characterization of the aluminum
hydride present in the compound of the invention next to a tungsten
hydride comprises a reaction for the deuteration of said compound.
The test can be carried out by bringing the compound according to
the invention into contact with a deuterium atmosphere under an
absolute pressure of 66.7 kPa, at a temperature chosen between 25
and 80.degree. C., preferably equal to 60.degree. C., for a period
of time of 15 minutes. A selective deuteration reaction is thus
carried out under these conditions: it makes it possible to
substitute the hydrogen atoms by deuterium atoms in the W--H bonds
and to thus form new W-D bonds which, by infrared spectroscopy,
exhibit two absorption bands at 1293 and 1393 cm.sup.-1, while
leaving unchanged the hydrogen atoms in the Al--H bonds which can
then be characterized, by infrared spectroscopy, by an absorption
band at 1914 cm.sup.-1.
The present invention also relates to a process for the preparation
of the supported metal compound. The compound according to the
invention, which exists essentially in the form of a tungsten
hydride grafted to a support based on aluminum oxide, can be
prepared by a process comprising the following stages:
(1) a stage in which an organometallic tungsten precursor (Pr) is
dispersed over and grafted to a support based on aluminum oxide, in
which precursor the tungsten is in particular bonded or complexed
to at least one hydrocarbon ligand, so as to form a tungsten
hydrocarbon compound or complex grafted to said support, then
(2) a stage of hydrogenolysis of the grafted tungsten hydrocarbon
compound or complex resulting from the preceding stage, so as to
form a tungsten hydride grafted to said support.
The organometallic tungsten precursor Pr preferably comprises a
tungsten atom bonded or complexed to one or more hydrocarbon
ligands. The tungsten atom can in particular be bonded to a carbon
of the hydrocarbon ligand via carbon-tungsten single, double or
triple bonds. The hydrocarbon ligands can be identical or
different, saturated or unsaturated, hydrocarbon radicals, in
particular aliphatic or alicyclic hydrocarbon radicals, preferably
C.sub.1 to C.sub.20 radicals, in particular C.sub.1 to C.sub.10
radicals, and can be chosen in particular from the hydrocarbon
radicals R described above. The number of hydrocarbon ligands
bonded to the tungsten atom depends on the degree of oxidation of
the tungsten in the precursor Pr and can be at most equal to the
degree of oxidation of the tungsten in the precursor Pr, in
particular be greater than 0 and at most equal to the maximum
degree of oxidation of the tungsten and preferably have any value
ranging from 2 to 6, in particular from 4 to 6.
The precursor Pr can comprise a tungsten atom in particular
complexed to one or more hydrocarbon ligands such that the degree
of oxidation of the tungsten is equal to 0. The hydrocarbon ligand
can be chosen from aromatic ligands or carbonyl ligands. Thus, the
precursor Pr can be chosen from tungsten bisarene and tungsten
hexacarbonyl.
Prior to the first dispersing and grafting stage, the support based
on aluminum oxide can be subjected to a preliminary stage of
calcination and/or of dehydroxylation. The support can be calcined
so as to oxidize the carbon possibly present in the support and to
remove it in the form of carbon dioxide. The calcination can be
carried out by subjecting the support to an oxidizing heat
treatment, in particular under a stream of dry air, at a
temperature lower than the sintering temperature of the support,
for example at a temperature ranging from 100 to 1000.degree. C.,
preferably from 200 to 800.degree. C., for a sufficient period of
time which makes it possible to remove the carbon dioxide and which
can range from 0.1 to 48 hours, under a pressure of less than,
equal to or greater than atmospheric pressure.
The support can also be subjected to another preliminary stage,
referred to as dehydroxylation. This stage can be carried out so as
to optionally remove the residual water from the support and a
portion of the hydroxyl groups, to leave behind, in particular at
the surface of the support, a residual amount of the hydroxyl
groups and to optionally form aluminoxane bridges (of formula
Al--O--Al). The dehydroxylation can be carried out by subjecting
the support to a heat treatment under an inert gas stream, for
example under a stream of nitrogen, of argon or of helium, under a
pressure preferably of less than atmospheric pressure, for example
under an absolute pressure ranging from 10.sup.-4 Pa to 10.sup.2
kPa, preferably from 10.sup.-2 Pa to 50 kPa, at a temperature of
less than the sintering temperature of the support, for example at
a temperature ranging from 100 to 1000.degree. C., preferably from
200 to 800.degree. C., and for a sufficient period of time which
makes it possible to leave an appropriate residual amount of
hydroxyl and/or aluminoxane groups in the support and which can
range from 0.1 to 48 hours. The dehydroxylation stage can
advantageously be carried out after the calcination stage.
The dispersing and grafting stage can be carried out by
sublimation, by impregnation using a solvent or by dry mixing. In
the case of a stage by sublimation, the precursor Pr, which
generally exists in the solid state under standard conditions, is
heated, in particular under a pressure of less than atmospheric
pressure and under temperature conditions which provide for its
sublimation and its migration in the gaseous state over the
support. The sublimation can be carried out at a temperature
ranging from -30 to 200.degree. C. and in particular under an
absolute pressure ranging from 10.sup.-4 to 1 Pa. The grafting of
the precursor Pr to the support can be monitored by infrared
spectroscopy. The excess precursor Pr which has not grafted to the
support can be removed by reverse sublimation.
The dispersing and grafting stage can also be carried out by
impregnation using a solvent. In this case, the precursor Pr can be
dissolved in a polar or nonpolar organic solvent, for example
pentane or ethyl ether. The impregnation can be carried out by
bringing the support based on aluminum oxide into contact with the
solution, prepared beforehand, of the precursor Pr. The
impregnation can be carried out at a temperature ranging from -80
to 200.degree. C., under an inert atmosphere, for example an
atmosphere of nitrogen, of argon or of helium, and preferably with
stirring. A suspension of a tungsten hydrocarbon compound or
complex grafted to the support is thus obtained. The excess
precursor Pr which has not grafted to the support can be removed by
washing using an organic solvent identical to or different from
that used during the impregnation.
The dispersing and grafting stage can also be carried out by dry
mixing, in particular by dry mechanical mixing, in the absence of
liquid or of liquid solvent. In this case, the precursor Pr, which
is present in the form of a solid, is mixed with the support based
on aluminum oxide in the absence of liquid or of liquid solvent, in
particular with mechanical stirring and under an inert atmosphere,
for example an atmosphere of nitrogen, of argon or of helium, so as
to form a mixture of two solids. During or after the dry mixing, it
is possible to carry out a heat treatment and/or a treatment under
a pressure of less than atmospheric pressure, so as to bring about
the migration and the reaction of the precursor Pr with the
support. The precursor which has not been grafted to the support
can be removed by reverse sublimation or by washing using an
organic solvent.
The preparation of the compound according to the invention can
comprise a second stage referred to as hydrogenolysis. It is a
reaction for the hydrogenolysis of the tungsten hydrocarbon
compound or complex grafted to the support as prepared in the
preceding stage. The reaction is generally carried out so as to
form a tungsten hydride grafted to the support. The term
"hydrogenolysis" is understood to mean, generally, a reaction in
which a molecule is cleaved with attachment of hydrogen to the two
cleaved portions. To be specific, the cleavage reaction takes place
in particular between the tungsten atom grafted to the support and
the carbon atom of the precursor Pr attached to or complexed with
said tungsten atom. The hydrogenolysis can be carried out using
hydrogen or a reducing agent capable in particular of converting
the grafted tungsten hydrocarbon compound or complex to grafted
tungsten hydride. The hydrogenolysis can be carried out by bringing
the grafted tungsten hydrocarbon compound or complex into contact
with hydrogen or the reducing agent. It can be carried out under a
hydrogen atmosphere or an inert atmosphere, when a reducing agent
is used, under an absolute pressure ranging from 10.sup.-2 to 10
MPa, at a temperature ranging from 20 to 500.degree. C., for a
period of time ranging from 0.1 to 48 hours.
The present invention furthermore relates to the use of the
supported metal compound according to the invention and as
disclosed in FR 03 03588 in a process employing cleavage and
recombination reactions of Csp.sup.2.dbd.Csp.sup.2 olefinic double
bonds to manufacture novel olefins. It relates more particularly to
the use of the compound according to the invention as catalyst in
reactions for the metathesis of an olefin with itself
(self-metathesis) or with at least one other olefin (crossed
metathesis) as represented in the above equations (1) and (2).
The following examples illustrate the present invention.
EXAMPLE 1
Preparation of a Tungsten Hydride Grafted to an Alumina
In a preliminary stage, 530 mg of a .gamma.-alumina, having a mean
size of 40 .mu.m and a specific surface (B.E.T.) of 200 m.sup.2/g,
comprising 90% by weight of alumina and 9% by weight of water and
sold by Johnson Matthey (Great Britain), are subjected to a
calcination treatment under a stream of dry air at 500.degree. C.
for 15 hours and then to a dehydroxylation treatment under an
absolute pressure of 10.sup.-2 Pa at 500.degree. C. for 15 hours,
so that the alumina thus calcined and dehydroxylated exhibits, by
infrared spectroscopy, three absorption bands respectively at 3774,
3727 and 3683 cm.sup.-1 characteristic in particular of residual
AlO--H bond.
In a first stage, the 530 mg of the alumina prepared above are
introduced into a glass reactor under an argon atmosphere and at
25.degree. C., followed by a solution of 6 ml of n-pentane
comprising 300 mg of tris(neopentyl)neopentylidynetungsten, used as
precursor Pr and corresponding to the general formula:
W[--CH.sub.2--C(CH.sub.3).sub.3].sub.3[.ident.C--C(CH.sub.3).sub.3]
(3)
The mixture thus obtained is maintained at 25.degree. C. for 3
hours. At the end of this time, a tungsten organometallic compound
grafted to the alumina is obtained, the excess precursor Pr which
has not reacted being removed by washing with n-pentane at
25.degree. C. The tungsten organometallic compound thus grafted is
dried under vacuum. It comprises 1.5% by weight of tungsten and
corresponds to the general formula:
(Al--O).sub.xW[--CH.sub.2--C(CH.sub.3).sub.3].sub.y[.dbd.CH--C(CH.sub.3).-
sub.3] (4) with x=1 and y=2.
In a second stage, 50 mg of the grafted tungsten organometallic
compound obtained above are isolated and subjected in a glass
reactor to a hydrogenolysis treatment by bringing into contact with
hydrogen under an absolute hydrogen pressure of 73 kPa at
150.degree. C. for 15 hours. At the end of this time, the reactor
is cooled to 25.degree. C. and a compound (W/Al-1) according to the
invention, which comprises in particular a tungsten hydride grafted
to the alumina, is obtained and isolated under argon. The compound
(W/Al-1) comprises 1.5% by weight of tungsten and exhibits, by
infrared spectroscopy, two absorption bands respectively at 1903
and 1804 cm.sup.-1 characteristic of the W--H bond grafted in
particular to the alumina.
EXAMPLE 2
Preparation of a Tungsten Hydride Grafted to an Alumina
The preliminary stages of calcination and of dehydroxylation of the
.alpha.-alumina are absolutely identical to those of example 1.
In a first stage, 53 mg of the alumina prepared above are isolated
and introduced into a glass reactor at 25.degree. C. under an argon
atmosphere. The precursor Pr of general formula (3) as used in
example 1 is then introduced into the reactor. The reactor is then
heated at 70.degree. C. for 2 hours, so as to sublime the precursor
Pr over the alumina and to form a tungsten organometallic compound
grafted to the alumina. At the end of this time, the excess
precursor Pr which has not reacted is removed by reverse
sublimation at 70.degree. C. Subsequently, the reactor is cooled to
25.degree. C. and a tungsten organo-metallic compound thus grafted
which comprises 3.7% by weight of tungsten and which corresponds to
the preceding general formula (4) is isolated under argon.
The second stage is carried out exactly as in example 1, except for
the fact that use is made of the tungsten organometallic compound
grafted to the alumina prepared in the preceding stage. A compound
(W/Al-2) according to the invention comprising a tungsten hydride
grafted to the alumina and comprising 3.7% by weight of tungsten is
thus obtained. It exhibits, by infrared spectroscopy, two
absorption bands respectively at 1903 and 1804 cm.sup.-1
characteristic of the W--H bond grafted in particular to the
alumina.
The compound (W/Al-2) is subjected to a selective deuteration test
which shows that it comprises a tungsten hydride and an aluminum
hydride, both grafted to the alumina. A sample of the compound
(W/Al-2) is placed in a glass reactor and is then brought into
contact, in this reactor, with a deuterium atmosphere under an
absolute pressure of 66.7 kPa at a temperature of 60.degree. C. for
15 minutes. At the end of this time, the reactor is cooled to
25.degree. C. and the solid compound thus deuterated is isolated
under argon; this compound exhibits, by infrared spectroscopy, an
absorption band at 1914 cm.sup.-1 characteristic of the Al--H bond
unchanged by the deuteration reaction carried out under these
conditions. Furthermore, it is observed that the absorption bands
at 1903 and 1804 cm.sup.-1 characteristic of the W--H bond grafted
to the alumina disappear to the advantage of the absorption bands
respectively at 1293 and 1393 cm.sup.-1 characteristic of the W-D
bond grafted to the alumina and formed by the deuteration reaction
of the W--H bonds.
EXAMPLE 3
Preparation of a Tungsten Hydride Grafted to an Alumina
The preliminary stages of calcination and of dehydroxylation of the
alumina are absolutely identical to those described in example
1.
In a first stage, 2 g of the alumina prepared above are isolated
and introduced under an argon atmosphere into a glass reactor at
25.degree. C. equipped with a magnetic stirring bar. 305 mg of the
precursor Pr of general formula (3) as used in example 1 are then
introduced into the reactor. The reactor is heated to 66.degree. C.
and the dry mixture thus prepared is stirred for 4 hours. At the
end of this time, the reactor is cooled to 25.degree. C. and then
the solid mixture is washed with n-pentane at 25.degree. C. The
solid compound thus washed is dried under vacuum and then isolated
under argon, so as to obtain a tungsten organometallic compound
grafted to the alumina comprising 3.9% by weight of tungsten and
corresponding to the preceding general formula (4).
The second stage is carried out exactly as in example 1, except for
the fact that use is made of the tungsten organometallic compound
grafted to the alumina prepared above. A compound (W/Al-3)
according to the invention comprising a tungsten hydride grafted to
the alumina and comprising 3.9% by weight of tungsten is thus
obtained. It exhibits, by infrared spectroscopy, two absorption
bands respectively at 1903 and 1804 cm.sup.-1 characteristic of the
W--H bond grafted to the alumina. Furthermore, it exhibits, by
nuclear magnetic resonance (solid .sup.1H NMR) at 500 MHz, a value
of the chemical shift of the tungsten hydride (.delta..sub.W--H)
equal to 10.6 ppm (parts per million).
EXAMPLE 4
Preparation of a Tungsten Hydride Grafted to a Silica/Alumina
In a preliminary stage, 530 mg of a silica/alumina, having a
specific surface (B.E.T.) of 475 m.sup.2/g, comprising 33% by
weight of alumina and sold by Akzo Nobel, are subjected to a
calcination treatment under a stream of dry air at 500.degree. C.
for 15 hours and then to a dehydroxylation treatment under an
absolute pressure of 10.sup.-2 Pa at 500.degree. C. for 15 hours,
so that the silica/alumina thus calcined and dehydroxylated
exhibits, by infrared spectroscopy, an absorption band at 3747
cm.sup.-1 characteristic in particular of residual SiO--H bond.
In a first stage, the 530 mg of silica/alumina prepared above are
introduced into a glass reactor under an argon atmosphere and at
25.degree. C., followed by a solution of 6 ml of n-pentane
comprising 300 mg of the precursor Pr of general formula (3) as
used in example 1.
The mixture thus obtained is maintained at 25.degree. C. for 3
hours. At the end of this time, a tungsten organo-metallic compound
grafted to the silica/alumina is obtained, the excess precursor Pr
which has not reacted being removed by washing with n-pentane at
25.degree. C. The tungsten organometallic compound thus grafted is
dried under vacuum. It comprises 1.5% by weight of tungsten and
corresponds to the general formula:
(Si--O).sub.xW[--CH.sub.2--C(CH.sub.3).sub.3].sub.y[.dbd.CH--C(CH.sub.3).-
sub.3] (5) with x=1 and y=2.
In a second stage, 50 mg of the grafted tungsten organometallic
compound obtained above are isolated and are subjected, in a glass
reactor, to a hydrogenolysis treatment by bringing into contact
with hydrogen under an absolute hydrogen pressure of 73 kPa at
150.degree. C. for 15 hours. At the end of this time, the reactor
is cooled to 25.degree. C. and a compound (W/SiAl-1) according to
the invention which comprises in particular a tungsten hydride
grafted to silica/alumina is obtained and isolated under argon. The
compound (W/SiAl-1) comprises 1.5% by weight of tungsten and
exhibits, by infrared spectroscopy, two absorption bands
respectively at 1906 and 1804 cm.sup.-1 characteristic of the W--H
bond grafted in particular to silica/alumina.
EXAMPLE 5
Preparation of a Tungsten Hydride Grafted to a Silica/Alumina
The preliminary stages of calcination and of dehydroxylation of the
silica/alumina are absolutely identical to those described in
example 3.
In a first stage, 1 g of the silica/alumina prepared above is
isolated and introduced under an argon atmosphere into a glass
reactor at 25.degree. C. equipped with a magnetic stirring bar. 305
mg of the precursor Pr of general formula (3) as used in example 1
are then introduced into the reactor. The reactor is heated at
66.degree. C. and the dry mixture thus produced is stirred for 4
hours. At the end of this time, the reactor is cooled to 25.degree.
C. and then the solid mixture is washed with n-pentane at
25.degree. C. The solid compound thus washed is dried under vacuum
and then isolated under argon, so as to obtain a tungsten
organometallic compound grafted to the silica/alumina comprising
7.5% by weight of tungsten and corresponding to the preceding
general formula (5).
The second stage is carried out exactly as in example 1, except for
the fact that use is made of the tungsten organometallic compound
grafted to the silica/alumina prepared above. A compound (W/SiAl-2)
according to the invention comprising a tungsten hydride grafted to
the silica/alumina and comprising 7.5% by weight of tungsten is
thus obtained. It exhibits, by infrared spectroscopy, two
absorption bands respectively at 1903 and 1804 cm.sup.-1
characteristic of the W--H bond grafted to the silica/alumina.
Furthermore, it exhibits, by nuclear magnetic resonance (solid
.sup.1H NMR) at 500 MHz, a value of the chemical shift of the
tungsten hydride (.delta..sub.W--H) equal to 10.6 ppm (parts per
million).
EXAMPLE 6
Reaction for the Metathesis of Propene Catalyzed by W/Al-3 in a
Static Reactor
The supported metal compound (W/Al-3) prepared according to example
3 is used in a reaction for the metathesis of propene which can be
represented by the following equation:
##STR00003##
The experiment is carried out in the following way: the supported
metal compound is prepared "in situ" in a glass reactor as
described in example 3. The reactor is subsequently placed under
vacuum, then filled with propene up to a pressure of 76 kPa and,
finally, heated at 150.degree. C. The formation is then observed of
a mixture essentially of ethylene, of n- and isobutenes, and also
of pentenes and hexenes in smaller amounts, which are analyzed and
quantitatively determined by gas chromatography (capillary column
KCl/Al.sub.2O.sub.3, 50 m.times.0.32 mm; detection by flame
ionization).
The cumulative conversion of propene, which is the number of moles
of propene converted with respect to the number of moles of propene
introduced initially, and the number of rotations (T.O.N.) or
cumulative number of moles of propene converted over time per mol
of tungsten of the supported metal compound are calculated.
The selectivities (SC.sub.2), (SC.sub.4), (SC.sub.5) and (SC6) for
the various products are also calculated respectively according to
the following equations: SC.sub.2=(number of moles of ethylene
formed)/(total number of moles of olefins formed) SC.sub.4=(number
of moles of n-butenes formed)/(total number of moles of olefins
formed) SC.sub.5=(number of moles of pentenes formed)/(total number
of moles of olefins formed) SC6=(number of moles of hexenes
formed)/(total number of moles of olefins formed)
The results of the measurements and calculations defined above for
the reaction for the metathesis of propene as a function of the
time are collated in table 1 below.
TABLE-US-00001 Selectivities of the products formed (%) Cumulative
SC.sub.2 SC.sub.4 SC.sub.5 SC.sub.6 Time conversion ethylene
butenes pentenes hexenes (h) (%) T.O.N. (%) (%) (%) (%) 0 0 0 0 0 0
0 0.33 32.8 481 50.6 47.3 1.87 0.23 0.75 38.43 565 51.88 45.6 2.21
0.28 1.33 41.26 600.6 49.46 47.37 2.92 0.43 2 41.8 605.6 48.5 47.76
3.24 0.62 3 42.5 611 46.75 49.33 3.3 0.62
Metathesis of propene in a static reactor catalyzed by
WH/.alpha.-alumina (W/Al-3) at 150.degree. C.; M cat=50 mg (%
W=3.86%), V reactor=505 ml, P propene=76 kPa Propene/Ws=1470
EXAMPLE 7
Reaction for the Metathesis of Propene Catalyzed by W/Al-3 in a
Static Reactor
The experiment is carried out in a similar way to example 6, except
that the reaction is carried out at 80.degree. C.
The results of the measurements and calculations as defined in
example 6 for the reaction for the metathesis of propene as a
function of the time are collated in table 2 below.
TABLE-US-00002 Selectivities of the products formed (%) Cumulative
SC.sub.2 SC.sub.4 SC.sub.5 SC.sub.6 Time conversion ethylene
butenes pentenes hexenes (h) (%) T.O.N. (%) (%) (%) (%) 0.25 14.96
219 53.09 46.91 0 0 0.5 20.07 294 51.61 48.39 0 0 1 23.56 346 53.39
46.61 0 0 2 27.53 404 52.65 47.35
EXAMPLE 8
Reaction for the Metathesis of Propene Catalyzed by W/Al-3 in a
Dynamic Reactor
The complex
(Al--O).sub.xW[--CH.sub.2--C(CH.sub.3).sub.3].sub.y[.dbd.CH--C(CH.sub.3).-
sub.3] (4) grafted to the alumina by sublimation (200 mg; 3.86%
W/Al.sub.2O.sub.3; 42 micromol of W) according to example 3 is
transferred in a glove box into a tubular stainless steel reactor
which can be isolated from the atmosphere. After connecting the
reactor to the assembly, the circuit is purged with argon and then
the supported tungsten hydride catalyst [W].sub.s--H is prepared in
situ by treatment of the grafted alkyl-alkylidyne complexes under a
stream of hydrogen (3 ml/min) at 150.degree. C. for 15 h, resulting
in the compound (W/Al-3). After cooling to 25.degree. C., the
reactor is purged of the excess hydrogen with argon and then under
a stream of propene at 101.3 kPa (5 ml/min, i.e. a molar flow rate
of 5.31 propene/W/min). The reactor is then rapidly brought to the
temperature of 150.degree. C. (rise of 250.degree. C./h). The
products are analyzed on line by gas chromatography (capillary
column KCl/Al.sub.2O.sub.3, 50 m.times.0.32 mm; detection by flame
ionization). The formation is then observed mainly of ethylene, of
butenes, of pentenes and of hexenes in small amounts.
The results of the measurements and calculations as defined in
example 6 for the reaction for the metathesis of propene as a
function of the time are collated in table 3 below. In this case,
an instantaneous conversion, which is the number of moles of
propene converted with respect to the number of moles of propene
introduced at each instant, is defined.
TABLE-US-00003 Instan- Molar composition of the gas phase in %
taneous SC.sub.2 SC.sub.3 SC.sub.4 SC.sub.5 SC.sub.6 SC.sub.7
conver- Cumula- ethyl- pro- bu- pen- hex- hep- Time sion tive ene
pylene tenes tenes enes tenes (h) (%) T.O.N. (%) (%) (%) (%) (%)
(%) 0 0 0 0 0 0 0 0 0 14 40 1784 18.5 60 19.6 1.44 0.4 0.07 31 39.3
3950 18.6 60.7 19 1.25 0.33 0.06 48 38.7 6117 18.6 61.3 18.7 1.15
0.28 0.05 65 38.4 8283 18.5 61.6 18.4 1.07 0.26 0.046 114 37.5 14
528 18.31 62.5 18 0.93 0.21 0.037 148 37.7 18 861 18.1 62.3 18.5
0.87 0.2 0.033 182 36.44 23 194 18 63.56 17.4 0.82 0.18 0.031 203
36.24 25 870 17.95 63.76 17.28 0.79 0.17 0.029 213 36.1 27 144
17.87 63.9 17.2 0.78 0.17 0.029
EXAMPLE 9
Ethylene/2-Butene Crossed Metathesis Reaction Catalyzed by W/Al-3
in a Static Reactor
The experiment is carried out in a similar way to example 6, except
that the reaction is carried out at 150.degree. C. with a 50/50
molar mixture of ethylene and of 2-butene instead of propene.
Propene is then mainly formed according to the reaction:
##STR00004##
The results of the measurements and calculations as defined in
example 6 for the ethylene/2-butene crossed metathesis reaction as
a function of the time are collated in table 4 below.
TABLE-US-00004 Molar composition of the gas phase (%) Time C.sub.2
(%) C.sub.4 (%) C.sub.3 (%) C.sub.5 (%) C.sub.6 (%) (h) ethylene
butenes propene pentenes hexenes 0 55 45 0 0 0 0.25 39.28 30 30
0.64 0.04 0.75 28.58 24.68 45.93 0.7 0.1 1.25 24.1 21.8 52.07 1.13
0.15 2 21.78 20.71 56.05 1.27 0.17
EXAMPLE 10
Regeneration under Hydrogen of the Catalyst W/Al-3 in a Dynamic
Reactor
After having operated as in example 8, the catalyst (W/Al-3) is
regenerated in a dynamic reactor under a stream of hydrogen (4
ml/min, 0.1 MPa) at 150.degree. C. for 15 h. The catalyst, thus
regenerated, then regains its activity in the metathesis of
propene.
It should be clearly understood that the invention defined by the
appended claims is not limited to the specific embodiments
indicated in the above description but encompasses the alternative
forms thereof which depart neither from the scope nor from the
spirit of the present invention.
* * * * *